﻿using System;

namespace Dotnet.Utils.Utility.ObjectExtensions.Number
{
    public static class MathExtensions
    {
        public static double Erfc(double x)
        {
            return 1 - Erf(x);
        }

        public static double Erf(double x)
        {
            double a1 = 0.254829592;
            double a2 = -0.284496736;
            double a3 = 1.421413741;
            double a4 = -1.453152027;
            double a5 = 1.061405429;
            double p = 0.3275911;

            int sign = 1;
            if (x < 0)
                sign = -1;
            x = Math.Abs(x);
            double t = 1.0 / (1.0 + p * x);
            double y = 1.0 - ((((a5 * t + a4) * t + a3) * t + a2) * t + a1) * t * Math.Exp(-x * x);

            return sign * y;
        }
    }
}